I even just had a good idea how it could be implemented, we could use the existing USS instancing system. You're plodding along minding your own business in deep space (make a rule that these USSes don't occur within 5000ly of the bubble (more incentive to stay out there after satisfying prof Palin) because the lifeforms are shy) and have USS type 'biological signature detected', and when you pop in, bam! Random space whale.
I can't resist, here I go with another little story. Kinda how I imagine this is in the best possible implementation in the game.
I just clicked 5k ly from Lave, it had been a slow trip so far, I was contracted by an Alliance handler to find terraformable worlds, what are those Alliance guys up to, spreading out all over the place, best be careful they don't spread themselves too thin, especially after what happened at Ross 128...Still, a contract is a contract, so here I am.
At first I thought I was going space crazy, a signal contact, but different. I turned a little toward the source, the scanners started humming, then after a second or two; "Unknown Biological Signature". My first thought was Thargoids, and I felt my muscles tense around the stick, I wanted to turn back right now, but something tugged at me, I've seen Thargoids before, this was somehow different. I decided to take the risk, even with the exploration data on board, I dropped out of supercruise and looked around. Then I saw it.
Floating in space about 15k away was what I can only describe as an enormous space jellyfish, only it had a solid, shiny carapace, like a beetle, with whitish blue tentacles flowing beneath it's bulbous mass. I approached slowly, and as I reached about 10k away, it started moving. It was turning around. It was then I realised I was viewing it in profile, it turned toward my ship. Now I was looking at the round carapace straight on and couldn't see the tentacles. It was 'swimming' toward me. I wonder how it propels itself? As it approached, what I can only assume is a mouth began opening in the top center of the shell, I could see a mist being sucked in and out like breath, was it SMELLING me? It was still drawing closer, its 'mouth' pulsating. It didn't seem to be aggressive, so I held my ground. Show no fear.
It was now less than 1k away and filled my view. At a guess I'd say it was about the size of a Farragut, only wider because of the shell, I hadn't realised quite how big it was. At this point I started to regret my confidence, that mouth could easily swallow my DBX without touching the sides. I slowly applied some reverse thrust, but it moved closer still. Now I was starting to get really nervous. I flashed the ships lights on and off, it stopped, the carapace changed colour before my eyes, from the bluey brown it had been before to a deep purple, then suddenly a thousand illuminated 'spots' on the carapace all shone at once, it was blinding. Did this thing just flash me back? I decided to try the disco scanner, see what it would make of the honk, as the scanner charged, the illuminations immediately extinguished and the carapace turned grey brown again. BRRRRAAAAAAAAAAARRRRRRRRP. The creature backed off just a little but very quickly, it had retreated half a k in less than a second, but was still filling my view, and still far too close for me to jump away. Then it started to visibly inflate, it was definitely getting bigger, and new colours were playing on the surface of its shell. Eventually the 'shell' had become a flat disc where before it had been convex like an umbrella. I could see more of whatever was under the shell, it looked like the fins you would see on the underside of a mushroom, the glow of the tentacles and my own trepidation prevented me making a meaningful analysis, then suddenly, the ship pitched up hard. I was spinning through space, something had propelled me away, with great power. I reset the stabilisers and turned back toward the creature.
My sensors were on the fritz, was that an attack? I'm about 15k away again now and it's coming towards me again, faster this time. It could have been a greeting I suppose, if so, I wouldn't want to see the thing when it's upset! It was coming closer again. Right, time to go, enough close encounters for now. I started charging the FSD. Again the creature reacted, now it was right in front of me again, it must have covered 10 clicks in 2 seconds, wow, that thing is fast. Obviously I couldn't jump again due to the mass lock. The creature started inflating again. I immediately turned around and started flying away, but the creature followed me, blocking my path, again, and still inflating. It was much faster than my little DBX, there was no way I was going to outrun it. As it reached peak inflation, I knew what to expect and braced myself, but nothing happened. Then suddenly it opened its mouth again and a jet of something like liquid was ejected into space as it once again deflated. Once it had finished its 'eruption', it turned bright yellow with flashes of green and illuminated it's spots again, just for an instant. It was turning away from me now, I had a feeling that it was saying goodbye, so I instinctively flashed the ship lights again. It flashed its spots again. I flashed again, it flashed its spots again, we were communicating! Then just like that, it disappeared. I can only assume it warped off somewhere, but there was no wake or evidence that anything had ever been here. I started thinking I was going space crazy again, that I would wake up any minute having fallen asleep at the controls of the SRV, but no, this really happened.
I turned the scanners to the liquid ejection, only it wasn't liquid any more it had now solidified and broken up into small crystals. The scanners were taking their time with the analysis, I was almost hoping I would be the discoverer of a new compound, but no such luck. It was however a rich alloy of various rare and (inappropriately named) rare 'earth' metals, the refinery can sort these out I thought as I collected them up, but that would have to wait til this contract was done. Hope all the space whales are this friendly.